It's not so easy. The answer 302 simply means that the content is temporarily in a different place. This can happen on a regular website, and this does not always happen on a parked website.
I worked in an ISP with over 20,000 parked domains, and we did not use 302 on any of them.
I don’t think you will find a 100% solution for this. Even if you checked the page for phrases such as “Buy this domain” and “This domain can be sold”, you won’t know for sure.
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